A dialysis machine is used as a substitute for the natural kidney functions of a human body. As such, the dialysis machine cleans the blood of the natural accumulation of bodily wastes by separating the wastes from the blood outside or extracorporeally of the body. The separated wastes are discharged and the cleansed blood is returned to the body.
A dialysis machine uses a dialyzer to separate the wastes from the blood. The dialyzer includes a porous membrane located within a closed housing which effectively separates the housing into separate blood and dialysate compartments. The blood removed from the patient flows through the blood compartment, while a prepared solution of dialysate is passed through the dialysate compartment. The wastes from the blood pass through the membrane by osmosis, ionic transfer or fluid transport into the dialysate and, depending upon the type of dialysis treatment, desirable components from the dialysate may pass in the opposite direction through the membrane and into the blood. The transfer of the wastes into the dialysate cleanses the blood while allowing the desired components from the dialysate to enter the bloodstream.
The transfer of blood between the patient and the dialyzer occurs within a disposable blood tubing set. The blood tubing set and the dialyzer represent a closed extracorporeal path through which the patient's blood travels. The blood tubing set includes an arterial line for drawing blood from a patient, a venous line for returning blood to the patient, and a number of other lines for connecting the arterial and venous lines to the dialyzer and a blood pump.
Two types of dialyzers commonly used in dialysis treatments include the hollow fiber dialyzer and the plate dialyzer. The hollow fiber dialyzer is typically formed from a cylindrical housing having a bundle of hollow microporous fibers extending between opposing ends of the housing. The microporous nature of the fibers allows blood to flow through the hollow interior of the fibers without passing through the walls of the fibers. The hollow fibers are sealed or potted at each end of the housing so that the open ends of the hollow fibers communicate with a blood manifold at each end of the housing, one manifold connected to a blood inlet and the other manifold connected to a blood outlet. The interior volume of the hollow fibers between the inlet and outlet manifolds thus collectively comprise the blood compartment of the dialyzer. A separate inlet and outlet on the cylindrical housing (between the blood manifolds) provides access for dialysate to enter and exit the cylindrical housing. The dialysate enters the housing through the inlet and flows around the hollow fibers in the area between the sealed blood manifolds. The area within the housing between the manifolds which is not consumed by the hollow fibers thus comprises the dialysate compartment. The microporous nature of the hollow fibers allows for the exchange of wastes and other desired components between the blood and the dialysate. The used dialysate is then pumped from the dialyzer while the cleansed blood is collected within the outlet manifold and returned to the patient.
The plate dialyzer typically includes a rectangular housing within which a plurality of membrane plates are stacked together, or within which a single membrane is folded over upon itself a number of times, so that the blood and dialysate compartments are defined on opposite sides of the adjoining plates. A blood inlet and outlet are positioned to communicate with the respective sides of the plates that define the blood compartment, while a dialysate inlet and outlet are positioned to communicate with the dialysate compartment defined by the opposite sides of the plates.
Although the hollow fiber dialyzer is typically more expensive to manufacture than the plate dialyzer, the hollow fiber dialyzer is used predominantly in the United States because it can be cleaned and reused with a single patient a number of times, thereby reducing the effective cost of each dialysis treatment. Due to the intricate flow path between the plates of a plate dialyzer, it is not currently feasible to clean and reuse a plate dialyzer. The cost per dialysis treatment is thus higher with a plate dialyzer than with a reusable hollow fiber dialyzer. However, in countries where a patient's dialysis treatment is subsidized or paid for by the government, plate dialyzers may frequently be used and disposed of as medical waste after each treatment. Additionally, as the cost of plate dialyzers drops, and due to other concerns associated with cleaning hollow fiber dialyzers (e.g., the man hours required to clean the dialyzers and environmental concerns relating to the chemical sterilants used in cleaning the dialyzers), the popularity of plate dialyzers has recently risen. Therefore, to provide hospitals and dialysis clinics with the freedom to choose the type of dialyzer which best suits their needs, and to provide them with the flexibility to change their choice as their needs change, it will be increasingly important for dialysis machines to accommodate both types of dialyzers. Furthermore, it is desireable for dialysis machines to accomodate other types of devices used in extracorporeal treatments, for example a hemo-perfusion cartridge or filter.
Present dialysis machines are typically designed to hold only one type of dialyzer, usually either a hollow fiber or a plate dialyzer. For example, the majority of dialysis machines sold in the United States include a simple receptacle for holding a hollow fiber dialyzer and do not include any means for conveniently holding a plate dialyzer. Force fitting a rectangular plate dialyzer into a receptacle for a cylindrical hollow fiber dialyzer could lead to a serious accident should the plate dialyzer become dislodged and damaged during treatment.
Some dialysis machines have been retrofitted to remove the receptacle for a hollow fiber dialyzer and replace it with a receptacle for a plate dialyzer (or vice-versa). However, such a replacement is difficult and is usually only undertaken when a hospital or dialysis clinic that has used substantially only one type of dialyzer converts to using the other type of dialyzer. Replacing or converting the dialyzer holders on each dialysis machine would not be feasible for clinics that may routinely use both types of dialyzers. Alternatively, some dialysis machines have been retrofitted with a second attachment device for holding a plate dialyzer or a hollow fiber dialyzer. However, these type of aftermarket fixes do not typically function well and, furthermore, producing both types of dialyzer holders represents an extra cost to dialysis machine manufacturers.
Thus, while a number of different types and sizes of dialyzers are currently available for use in dialysis treatments, hospitals and clinics are not always able to benefit from these advances due to the incompatibility of existing dialysis machines with the new dialyzers. Additionally, a similar incompatibility may exist with other types of devices used in extracorporeal treatments (e.g., a hemo-perfusion cartridge).
These and other considerations have contributed to the evolution of the present invention which is summarized below.